Our long term goal is to determine the nature of functional or structural reorganization that occurs in the primate spinal cord following anterolateral cordotomy, and to correlate these changes with loss and subsequent recovery of sensory function. Such delayed recovery of sensory function occurs commonly in humans following an initially successful cordotomy. Experimental work will center upon a search for change in neuronal connectivity within the spinal dorsal horn. Research on the neural reconnectivity of the primate dorsal horn has already been funded under NIH grant #NS14899. The immediate goal is to create a model of neural reorganization after cordotomy in the rat, using anatomic, physiologic, and immunocytochemical techniques applicable to the primate experiments, but without reference to behavioral changes. This model may indicate the most fruitful investigative techniques to be used in the monkey rapidly and at relatively low cost. Initial emphasis will be placed upon demonstrating differences between control and experimental animals in (1) the central arborization patterns of primary afferent fibers, and (2) the immunocytochemical staining patterns of peptides within the dorsal horn. The completeness of spinothalamic tract section and the extent of ipsilateral spinothalamic tract projections will be assessed through retrograde HRP studies. In the future, the techniques that seem most promising in the rat model will be emphasized in the primate experiments. Changes in functional or structural organization of the primate dorsal horn will be correlated with loss and recovery of sensory function after cordotomy, through behavioral testing parameters already in use in this laboratory. This project provides an ideal opportunity for the candidate to pursue her research interests, while learning anatomic, physiologic, and immunocytochemical investigational techniques.